The present invention relates to an attachment mechanism and in particular a mechanism for releasably attaching two or more parts of surgical apparatus.
There are a large number of times when it may be desirable to temporarily attach two parts of a surgical apparatus together. For example, one part may be universal while another part may be patient or procedure specific or otherwise need to be varied depending on circumstance during an operation. The parts should be attachable with sufficient reliability that they will not come apart during normal use, so that the surgeon does not need to use one or more hands to keep the parts together, while being easily detachable so that time is not wasted during surgery manipulating or otherwise handling complex or fiddly attachment mechanisms.
It is also beneficial if such attachment mechanisms are simple to manufacture, clean after use and are useable with a wide variety of instruments, devices, parts, tools or other surgical devices.
One example of a releasable attachment mechanism is a bayonet type fastening as used to releasably attach markers to bone pins to allowing tracking of bones using various optical tracking systems. However, they are not entirely easy to handle, for example when wet or when wearing surgical gloves, and include multiple moving parts and so are complicated to manufacture and can trap debris making them harder to clean.
Releasable attachment mechanisms can also be used in connection with implant trial components. For example, prosthetic knee joints can include multiple parts which engage and articulate against each other via articulating surfaces, e.g., the condyles of a prosthetic femoral component and the articulating surface of a tibial component. During a surgical procedure, a surgeon often makes a number of bone cuts to prepare the surgical site to accept the prosthetic components. During a trialing stage, the surgeon may place a number of trail components within the surgical site to determine the appropriate dimensions, e.g. size, of the actual prosthetic components to be used to replace the joint. The actual prosthetic components themselves are not used, in order to prevent them being damaged and in case the surgeon selects an inappropriately sized component initially.
One example of the use of trial components, in a knee procedure, is to use a trial tibial component, such as a tibial tray, which includes a tibial articular surface. Various different sized trial components, in the medial-lateral direction, can be used depending on the size of the resected tibial surface. Depending on the height of the tibial cut, and also the femoral component and its position on the femur owing to the femoral cuts, the gap in the knee joint may vary. Also, the size of the gap in the knee joint may vary owing to soft tissue issues such as owing to the ligaments. In order to modify the gap between the tibial and femoral components, one or more shims of different thicknesses may be placed between an underside of the tibial tray and the resected tibial surface in order to reduce the gap between the tibial component and the femoral component.
However, there are difficulties in handling the tibial tray and shims in the operating theatre environment. Bodily fluids and debris from the surgical site can make the handling and manipulation of the tray and/or shims difficult. Further, articulation of the joint with the trial in place, for example to measure the gap in flexion and extension, places the joint components under various forces which could dislodge the trial components.
It would therefore be beneficial to provide a simple and easy to use mechanism to improve the ease and reliability of releasably attaching parts of an orthopaedic apparatus, particularly during a surgical procedure.